<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>bootstrap栅格系统</title>
    <link rel="stylesheet" href="./bootstrap/css/bootstrap.css">
    <style>

        .box {
            background-color: pink;
        }

        .box .row div {
            background-color: red;
        }
    </style>
</head>
<body>
<!-- container表示版心居中 -->
<div class="box container">
    <!-- row表示行，flex布局 -->
    <div class="row">
        <!--
            col-xl-3表示：
            栅格系统，表示在xl屏幕下，一个屏幕分为12份，当前元素占3份。也就是一行能够排列4个元素
         -->
        <div class="col-xl-3 col-lg-6 col-sm-12">1</div>
        <div class="col-xl-3 col-lg-6 col-sm-12">2</div>
        <div class="col-xl-3 col-lg-6 col-sm-12">3</div>
        <div class="col-xl-3 col-lg-6 col-sm-12">4</div>
    </div>

</div>

</body>
</html>
